The present invention relates to an acceleration sensing unit including an acceleration sensor element emitting an electric signal at a signal output and an assembly including such a sensing unit and a control unit.
For the precise magnetic detection of the rotational speed of a wheel in electronic motor vehicle brake systems, high-quality wheel speed sensor modules in chip technology are required, as they are described in German patent application P 44 45 120 (P 7805) or in DE-A-199 226 72 (P 9641). The wheel speed sensor modules described comprise a magneto-resistive element used to scan the magnetic field of a magnetic encoder rotating with the wheel. The modules are electrically active, with the result that the detected wheel speed data can be transmitted by way of a current interface to an integrated brake control unit in a fashion that is largely irrespective of the air slot.
DE-A-38 09 886 discloses a combination sensor for detecting the wheel speed and accelerations, wherein the necessary sensors are grouped in one joint uniform housing. The rotational speed sensor element incorporated in the combination sensor is an inductive or magneto-resistive transducer. The acceleration sensor has an inert precise mechanical mass whose movement indicates the prevailing acceleration. The sensor data is transmitted by way of a multi-core line that can be used jointly by both sensors. Consequently, the combination sensor described is no active sensor wherein the electric energy required by the sensor for operation is provided by a control unit intended to receive the signals by way of the signal lines.
An object of the present invention is to provide a sensing unit for detecting accelerations that is improved structurally, electrically and under signal technology aspects and optimized for the rough operation in the motor vehicle, while allowing low-cost manufacture in addition.